The newest trail open in the San Dieguito River Park is visible from Interstate 5 where it loops around the eastern end of the restored San Dieguito Lagoon.

Now named the Dust Devil Nature Trail, this 1.7-mile loop trail is easy, short and flat and a fine urban location for birding. Its terrain isn’t the most beautiful in our county, but it does offer a look at years of work that restored the vital lagoon.

Begin from the trailhead just off El Camino Real by heading north on the 0.7-mile North Loop, which connects to the 0.6-mile West Loop as well as the 0.4-mile East Loop. You’ll see acres of plantings and other man-made improvements that have helped to make the lagoon a productive, working estuary.

For years the lagoon’s mouth at the ocean had been allowed to plug with sand, effectively shutting off the natural tidal flow into the lagoon.

Since the dredging, natural tidal flows have been restored between the ocean and hundreds of acres of new and existing habitat that depend on daily seawater tidal influences, according to Southern California Edison, the lead on the San Dieguito Wetlands Restoration Project along with SDG&E.

Members of the San Dieguito River Valley Conservancy and the San Dieguito River Park also contributed, as did scientists from UC Santa Barbara.

The project began in 1988 when plans began to restore the San Dieguito Lagoon, located within the largest watershed (San Dieguito River) of the six San Diego coastal lagoons and was once the largest lagoon in the county.

According to a U.S. Coast and Geodetic Survey map from 1889, San Dieguito Lagoon and its surrounding wetlands once extended as far east as El Camino Real, and the surrounding valley floor was described as swamp and tidelands, according to the master plan for San Dieguito River Park and its Joint Powers Authority.

The lagoon, as are all lagoons, is a nursery for many oceanic fish, including California halibut and diamond turbot. Some fish live their entire lives in the estuarine environment, including an- chovies and topsmelt, which are food for many waterfowl.

Endangered birds that use San Dieguito Lagoon wetlands include the light-footed clapper rail, Belding’s savannah sparrow, California brown pelican, California least tern and western snowy plover. It’s also a critical stopover on the Pacific Flyway for many birds, including Canada geese.

Scientists have documented nearly a tripling of bird species in the lagoon since restoration began in 2006, according to SoCal Edison. The $90 million project was completed in late 2011.

Edison, SDG&E, and the city of Riverside’s Public Utilities Department chose the lagoon restoration project to meet requirements to lessen the effect on marine fish populations from the San Onofre Nuclear Generating Station. It is one of the largest coastal restoration projects on the West Coast.

Some 2 million yards of earth were excavated, much of which was moved from the mouth to the east of the lagoon, so that 116 acres of tidal wetlands were created on both sides of I-5. The excavation included the site of a former World War II Navy blimp landing field to the west of I-5.

Steve Schroeter of the Marine Science Institute at UC Santa Barbara is one of three principal investigators of the project, along with Mark Page and Dan Reed of the university. They continue to monitor the wetlands.

“The mud flats are really good bird habitat,” Schroeter told members of the San Dieguito River Valley Conservancy recently. “The white patches you see are nesting sites for endangered least terns, and we hope for snowy plovers, too.”

Some 13.7 acres of sandy nesting habitat has been created or restored for California least terns and snowy plovers. Least terns like shallow waters near estuaries, and they lay their eggs along sandy beaches near these waters. Sand spits and beaches at river mouths are favored nesting spots for the snowy plovers.

Biologists have monitored the area for a year since the project completion and “found that the wetland supports a promising population of snails, crabs, amphibians, small mammals, birds and provides fish a place to spawn and grow,” Edison says.

“Terrestrial animals have also become visible, such as the burrowing owl, cottontail rabbit and various reptiles.”

One area in the southern reaches still harbors eucalyptus trees and pampas grass, both considered invaders in the native coastal sage scrub habitat. These might someday be removed.

Also in the future, plans call for strategically placed trees or shrubs that will serve as blinds, allowing bird watching without disturbing the animals. Interpretive signs also are planned to explain the kinds of marsh visible from the trail.